1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device and particularly to a method for protecting a metal from being corroded by residual chlorine in a wiring process.
2. Description of the prior Art
Generally, A method for manufacturing semiconductor device forming a wiring is as follows.
First, a metal layer composed of aluminum or aluminum alloy is formed.
Next, a photoresist pattern is formed on the entire structure. Thereafter, using plasma including chlorine, a pattern of a wiring is formed by etching a metal layer which is exposed and a photoresist pattern is eliminated.
However, when a wiring is exposed to air, aluminum or aluminum alloy is corroded by residual chlorine. Therefore, four methods are conventionally used, to eliminate residual chlorine. The first method is cleaning the residual chlorine by deionized water. The second method is vaporizing residual chlorine using a thermal process.
The third method is encapsulating residual chlorine by forming a polymer on a metal layer, using CHF plasma, etc.
The fourth method is replacing residual chlorine by fluorine, using CF plasma. However, the first method cannot be protected against corrosion and the second method has problems such as hillocks, segregation, and recrystalization when the temperature is more than 300.degree. C.
The third method has the problem that the aluminum alloy of a wiring is corroded since the polymer is often broken, in the case where the wiring is exposed at air. The fourth method induces excessive damage of the oxide layer and undercut of the barrier metal layer such as TiN or TiW since over-etching using CF plasma is required so as to eliminate residual chlorine perfectly.
So, it is well known that by placing an oxygen plasma ash chamber in a metal etch apparatus, a photoresist layer is eliminated and simultaneously aluminum oxide is formed so as to protect a metal line from corrosion using a plasma in situ process before the wiring is exposed at air.
However, this method cannot effectively eliminate residual chlorine on a wiring.